The invention relates in general to a recording apparatus such as an inkjet printhead and, more specifically, to a printhead assembly that reduces the number of electrical interconnections in an inkjet printhead. More particularly, the invention relates to a shift register configuration that interleaves print data between upper and lower actuators in an inkjet printhead assembly.
Without limiting the scope of the invention, its background is described in connection with thermal inkjet printers, as an example.
Modern printing relies heavily on inkjet printing techniques. The term xe2x80x9cinkjetxe2x80x9d as utilized herein is intended to include all drop-on-demand or continuous inkjet printer systems including, but not limited to, thermal inkjet, piezoelectric, and continuous, all of which are well known in the printing industry. Essentially, an inkjet printer produces images on a receiver medium, such as paper, by ejecting ink droplets onto the receiver medium in an image-wise fashion. The advantages of non-impact, low-noise, low-energy use, and low cost operation, in addition to the capability of the printer to print on plain paper, are largely responsible for the wide acceptance of inkjet printers in the marketplace.
The printhead is the device that is most commonly used to direct the ink droplets onto the receiver medium. A printhead typically includes an ink reservoir and channels which carry the ink from the reservoir to one or more nozzles. Typically, sophisticated printhead systems utilize multiple nozzles for applications such as high-speed continuous inkjet printer systems, as an example. Continuous inkjet printhead device types include electrostatically controlled printheads and thermally steered printheads. Both printhead types are named according to the means used to steer ink droplets ejected from nozzle openings. It is well known in the art of inkjet printing that multiple actuators or heating elements per inkjet nozzle can be used. For example, U.S. Pat. No. 4,751,531 describes the use of a two heater printing nozzle while U.S. Pat. No. 4,695,853 describes the use of a vertical array of 9 heating elements per nozzle. In order to optimize drop formation conditions, it is preferred to utilize independent control circuits for such multi-actuator print nozzle configurations.
At the same time, there are also practical limitations with respect to the number of layers necessary to implement the control circuits as well as limitations in the number of interconnections that are practical in order to make the design useful and operable. These type of design constraints require the use of serial shift registers to bring the print data to the printhead during printing. Between the stated design constraints and the desire to minimize interconnections lies an optimum solution for multi-actuated printheads.
Accordingly, what is needed is a way of minimizing interconnections in a multi-actuated thermal inkjet printer. A printhead assembly with minimal shift registers and interconnections in a multi-actuated printhead assembly would provide numerous advantages.
The present invention provides a solution to dealing with the task of minimizing the number of interconnections used in a multi-actuated configuration printhead. The invention provides a printhead assembly with a reduced number of electrical interconnections that decreases the number of signals that interface the printhead to the image rastoring electronics.
According to the invention, disclosed is a recording apparatus comprising a plurality of recording elements arranged in an array for recording of an image on a receiver medium and a plurality of actuators associated with each respective recording element, each actuator being separately drivable to affect recording by a respective recording element. A plurality of shift register stages are provided, each stage being associated with a respective actuator, each recording element being associated with different shift register stages, the shift register stages being adapted to shift data from one stage to a next stage to distribute data to the different stages so that data shifted into a stage associated with an actuator may be shifted into a stage associated with another actuator in the course of shifting data from stage to stage.
In one embodiment, the actuators comprise heater elements configured as upper and lower heaters about each of the nozzles. The heater elements can be arranged into upper and lower heaters and the shift register stages interleaved so that some are arranged to operate upper heaters and others are arranged to operate lower heaters. The plurality of interconnections provide upper and lower enable lines operably coupled to the heaters for operating the recording elements in connection with the upper and lower shift registers, respectively.
Further disclosed is an inkjet printhead comprising a plurality of nozzles having corresponding nozzle openings for delivering ink unto a specified receiver medium and a plurality of shift registers operably coupled to the actuators associated and adapted to cause ink to be delivered through the nozzles openings in the direction of the receiver medium. A print data driving means is operably coupled to the shift registers via a plurality of interconnections and the shift registers are interleaved to minimize the number of interconnections.
In one embodiment, the actuators comprise heaters designated as upper and lower heaters and the shift registers are interleaved so that some are arranged to operate upper heaters and others are arranged to operate lower heaters. The interconnections include data lines for delivering print data signal and clock lines for delivering timing signals to said lower and upper shift registers. The data lines are interleaved between upper shift registers and lower shift registers. The print data driving means is configured to operate the clock lines by transmitting a clock signal that causes upper and lower shift registers to shift data received over data lines and thereby operate the plurality of heaters.
Further disclosed is an inkjet printer comprising a printhead nozzle assembly with a plurality of nozzles, each of the nozzles comprising a nozzle opening through which ink in the form of ink drops is ejected. An ink supply system is configured to supply ink to the printhead nozzles assembly with data path and control electronics circuitry operably coupled to the printhead nozzle assembly for providing image data to the printhead nozzle assembly. The printer further comprises means for delivering the image data to the printhead nozzle assembly. The printhead nozzle assembly further comprises at least two heater elements, an upper heater and a lower heater, predisposed about each of the nozzles, the heater elements configured to actuate each of the nozzles for printing. The data path and control electronics circuitry comprises a plurality of shift registers configured to drive the nozzles by causing them to deliver ink in the direction of a receiver media. The data path and control electronics circuitry further comprises a print data driver operably coupled to the shift registers and configured to deliver print data at specified times to the shift registers in order to cause the nozzles to deliver ink at specified locations and at specified times on the receiver media.
A technical advantage of the present invention is a cost effective method of controlling a printhead assembly in a thermal inkjet printhead.
Another technical advantage includes optimum compromise between the length of shift registers and number of heaters to be controlled. In one standard printhead configuration, twenty 128-bit shift registers are able to operate a 1280 nozzle assembly.